System and method for robotic surgery

ABSTRACT

A robotic surgery method for cutting a bone of a patient includes characterizing the geometry and positioning of the bone and manually moving a handheld manipulator, the handheld manipulator operatively coupled to a bone cutting tool having an end effector portion, to cut a portion of the bone with the end effector portion. The handheld manipulator further comprises a manipulator housing and an actuator assembly movably coupled between the manipulator housing and the bone cutting tool. The method further includes causing the actuator assembly to automatically move relative to the manipulator housing to maintain the end effector portion of the tool within a desired bone cutting envelope in response to movement of the manipulator housing relative to the bone.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/276,099, filed Oct. 18, 2011, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to surgical systems, and morespecifically to systems and methods for positioning and orienting toolsduring surgical procedures.

BACKGROUND

Minimally invasive surgery (MIS) is the performance of surgery throughincisions that are considerably smaller than incisions used intraditional surgical approaches. For example, in an orthopedicapplication such as total knee replacement surgery, an MIS incisionlength may be in a range of about 4 to 6 inches, whereas an incisionlength in traditional total knee surgery is typically in a range ofabout 6 to 12 inches. As a result of the smaller incision length, MISprocedures are generally less invasive than traditional surgicalapproaches, which minimizes trauma to soft tissue, reducespost-operative pain, promotes earlier mobilization, shortens hospitalstays, and speeds rehabilitation.

MIS presents several challenges for a surgeon. For example, in minimallyinvasive orthopedic joint replacement, the small incision size mayreduce the surgeon's ability to view and access the anatomy, which mayincrease the complexity of sculpting bone and assessing proper implantposition. As a result, accurate placement of implants may be difficult.Conventional techniques for counteracting these problems include, forexample, surgical navigation, positioning the subject patient limb foroptimal joint exposure, and employing specially designed, downsizedinstrumentation and complex surgical techniques. Such techniques,however, typically require a large amount of specializedinstrumentation, a lengthy training process, and a high degree of skill.Moreover, operative results for a single surgeon and among varioussurgeons are not sufficiently predictable, repeatable, and/or accurate.As a result, implant performance and longevity varies among patients.

To assist with MIS and conventional surgical techniques, advancementshave been made in surgical instrumentation, and in technologies forunderstanding the spatial and rotational relationships between surgicalinstruments and tissue structures with which they are intervening duringsurgery. For example, instruments for calcified tissue intervention thatare smaller, lighter, and more maneuverable than conventionalinstruments have become available, such as handheld instrumentsconfigured to be substantially or wholly supported manually as anoperator creates one or more holes, contours, etc. in a subject bonytissue structure. In certain surgical scenarios, it is desirable to beable to use such handheld type instrumentation while understanding wherethe working end of the pertinent tools are relative to the anatomy. Inparticular, it is desirable to be able to control the intervention suchthat there are no aberrant aspects, wherein bone or other tissue isremoved outside of the surgical plan, as in a situation wherein asurgical operator has a hand tremor that mistakenly takes the cuttinginstrument off path, or wherein a patient moves unexpectedly, therebytaking the instrument off path relative to subject tissue structure.There is a need for handheld systems that are capable of assisting asurgeon or other operator intraoperatively by compensating for aberrantmovements or changes pertinent to the spatial relationship betweenassociated instruments and tissue structures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a handheld bone cutting tool adjacent various tissuestructures of the skeleton.

FIG. 1B illustrates a close in view of a handheld bone cutting tooladjacent a femur, both of which reside in a common global coordinatesystem.

FIG. 1C illustrates an embodiment wherein an optical tracking system isutilized to track one or more of a targeted tissue structure and acutting tool.

FIG. 1D illustrates an embodiment wherein an optical tracking system isutilized to track one or more of a targeted tissue structure and acutting tool, which may be coupled to a robotic arm.

FIG. 1E illustrates an embodiment wherein two mechanical trackerlinkages are utilized to monitor the spatial positions of a targetedtissue structure and an interventional tool.

FIG. 1F illustrates an embodiment wherein a mechanical tracker linkageis utilized to monitor the spatial relationship between a targetedtissue structure and an interventional tool.

FIG. 2A illustrates a desired bone cutting envelope relative to a tissuesubstrate.

FIG. 2B illustrates one variation of an attempted cutting enveloperelative to a tissue substrates and desired bone cutting envelope.

FIGS. 3A-3M illustrate aspects of a handheld tissue cutting toolfeaturing a motion compensation mechanism.

FIGS. 4A-4C illustrate aspects of process embodiments wherein amotion-compensated interventional tool may be utilized in a surgicalprocedure.

FIGS. 5A-5C illustrate aspects of process embodiments wherein amotion-compensated interventional tool may be utilized in a surgicalprocedure.

FIGS. 6A-6C illustrate aspects of embodiments wherein potential fieldsmay be utilized to further control motion of the interventional tool.

FIG. 7 illustrates aspects of an embodiment wherein potential fields maybe utilized to further control motion of the interventional tool.

SUMMARY

One embodiment is directed to a robotic surgery system for cutting abone of a patient, comprising: a handheld manipulator configured to bemanually moved in a global coordinate system relative to the bone, thehandheld manipulator comprising: a bone cutting tool comprising an endeffector portion, a frame assembly, and a motion compensation assemblymovably coupled to the frame assembly and bone cutting tool; and acontroller operatively coupled to the manipulator and configured tooperate one or more actuators within the frame assembly to cause themotion compensation assembly to automatically move relative to the frameassembly to defeat aberrant movement of the bone cutting tool that wouldplace the end effector portion of the tool out of a desired bone cuttingenvelope that is based at least in part upon one or more images of thebone, while allowing the bone cutting tool to continue cutting one ormore portions of the bone. The end effector portion may comprise a burr.The system further may comprise a housing coupled to the frame assembly.The housing may comprise a handle configured to be manually grasped by ahuman hand. The housing may be operatively coupled to a gravitycompensation mechanism. The frame assembly may comprise one or moremotors operatively coupled to one or more structural members, the one ormore structural members being coupled to the motion compensationassembly. The one or more structural members may be configured to insertand retract relative to the frame assembly, causing an associatedmovement of the motion compensation assembly. The one or more motors maybe operatively coupled to the one or more structural members via one ormore lead screw assemblies configured to insert and retract each of thestructural members in accordance with rotation of the one or moremotors. The system may further comprise one or more belts operativelycoupled between each of the one or more motors and one or more leadscrew assemblies, the one or more belts configured to transferrotational motion from the one or more motors to the one or more leadscrew assemblies. The system may further comprise one or more gearsintercoupled between at least one of the one or more lead screwassemblies and one or more motors, the gears configured to transferrotational motion from the one or more motors to the one or more leadscrew assemblies. The system may further comprise a tool drive assemblyintercoupled between the bone cutting tool and the motion compensationassembly. The tool drive assembly may comprise a motor configured toactuate the bone cutting tool. The motor may be configured tocontrollably move the bone cutting tool. The motor may be operativelycoupled to the controller such that the controller may control or stop acutting velocity of the bone cutting tool. The controller may beconfigured to change the cutting velocity of the bone cutting tool basedat least in part upon a signal from a sensor indicating that the endeffector portion is being moved toward a boundary of the desired bonecutting envelope. The controller may be configured to modulate thecutting velocity of the bone cutting tool based at least in part uponthe location of the tool within the desired bone cutting envelope. Thecontroller may be configured to generally reduce the cutting velocity ofthe bone cutting tool when the tool is moved adjacent an edge of thedesired bone cutting envelope. The controller may be configured tomodulate the cutting velocity of the bone cutting tool based at least inpart upon the location of the tool within a predetermined workspace ofthe handheld manipulator. The controller may be configured to generallyreduce the cutting velocity of the bone cutting tool when the tool ismoved adjacent the edge of the predetermined workspace. The system mayfurther comprise a tracking subsystem configured to determine a positionof the end effector portion of the bone cutting tool relative to theglobal coordinate system. The system may further comprise a trackingsubsystem configured to determine a position of one or more portions ofthe desired bone cutting envelope relative to the global coordinatesystem. The system may further comprise a tracking subsystem configuredto determine a position of the end effector portion of the bone cuttingtool relative to one or more portions of the desired bone cuttingenvelope. The tracking subsystem may comprise a tracking elementselected from the group consisting of: a mechanical tracker linkage, anoptical tracker, an ultrasonic tracker, and an ultra-wide-band tracker.The tracking system may comprise a mechanical tracker linkage having atleast two substantially rigid portions coupled by at least one movablejoint. The tracking system may comprise a mechanical tracker linkagehaving at least three substantially rigid portions coupled in a seriesconfiguration by two or more movable joints. The series configurationmay comprise a proximal end and a distal end, each of which is coupledto a kinematic quick-connect fitting. A proximal kinematic quick-connectfitting may be configured to be fixedly and removably coupled to thebone. A distal kinematic quick-connect fitting may be configured to befixedly and removably coupled to the frame assembly. The controller maybe configured to defeat aberrant movement of the bone cutting tool thatis associated with relatively high frequency unintended motion. Therelatively high frequency unintended motion may have a frequency betweenabout 1 Hz and about 12 Hz. The controller may be configured to defeataberrant movement of the bone cutting tool that is associated withrelatively low frequency unintended motion. The relatively low frequencyunintended motion may have a frequency between about 0 Hz and about 1Hz. The controller may be configured to defeat aberrant movement of thebone cutting tool that is associated with both relatively low frequencyunintended motion and relatively high frequency unintended motion. Theunintended motion may have a frequency between about 0 Hz and about 12Hz. The one or more images may be acquired using an imaging modalityselected from the group consisting of: computed tomography, radiography,ultrasound, and magnetic resonance. The controller may be configured tomodulate the tool path automatically based at least in part uponpotential field analysis. The controller may be configured to executemodulation of the tool path through motion compensation. The controllermay be configured to execute modulation of the tool path through hapticresistance to motion of the handheld manipulator.

Another embodiment is directed to a robotic surgery method for cutting abone of a patient, comprising: acquiring image information regarding thebone; manually moving a handheld manipulator, the handheld manipulatoroperatively coupled to a bone cutting tool having an end effectorportion, to cut a portion of the bone with the end effector portion; andautomatically compensating for aberrant movement of the bone cuttingtool that would place the end effector portion of the tool out of adesired bone cutting envelope that is based at least in part upon theimage information, while allowing the bone cutting tool to continuecutting one or more portions of the bone. The handheld manipulator maybe configured to be manually moved in a global coordinate systemrelative to the bone. The end effector portion may be configured to bemoved at a preferred bone cutting velocity. The method may furthercomprise modulating the cutting velocity based at least in part upon thelocation of the end effector portion within a desired bone cuttingenvelope. The method may further comprise generally reducing the cuttingvelocity of the end effector portion when the end effector portion ismoved adjacent an edge of a desired bone cutting envelope. The methodmay further comprise modulating the cutting velocity of the end effectorportion based at least in part upon the location of the end effectorportion within a predetermined workspace of the handheld manipulator.The method may further comprise generally reducing the cutting velocityof the end effector portion when the end effector portion is movedadjacent an edge of the predetermined workspace of the handheldmanipulator. The end effector portion may be allowed to continue cuttingone or more portions of the bone at the preferred cutting angularvelocity while automatically compensating for aberrant movement of thebone cutting tool. Automatically compensating for aberrant movement ofthe bone cutting tool may comprise controllably moving the cutting toolrelative to the handheld manipulator. Controllably moving may compriseaxially moving the cutting tool in a direction substantially coaxialwith a longitudinal axis of a previous position of the cutting tool.Controllably moving may comprise adjusting a pitch or yaw of the cuttingtool relative to a longitudinal axis of a previous position of thecutting tool. Controllably moving may comprise moving the cutting toolin two or more degrees of freedom. Acquiring image information maycomprise using an imaging modality selected from the group consistingof: computed tomography, radiography, ultrasound, and magneticresonance. The method further may comprise creating a preoperativesurgical plan based at least in part upon the image information, andutilizing the preoperative surgical plan to create the desired bonecutting envelope. Controllably moving the cutting tool relative to thehandheld manipulator may comprise operating a motor. Operating the motormay operate a lead screw mechanism operatively coupled to the motor. Themethod may further comprise determining that an attempted movement is anaberrant movement. Determining that an attempted movement is an aberrantmovement may comprise tracking the spatial positioning of the bone andthe end effector portion of the cutting tool. Tracking the spatialpositioning of the bone may comprise monitoring the positions of one ormore optical tracking markers that are coupled to the bone. Tracking thespatial positioning of the bone may comprise monitoring the positions ofone or more joints of a mechanical tracker linkage that is coupled tothe bone. Tracking the spatial positioning of the end effector portionof the cutting tool may comprise monitoring the positions of one or moreoptical tracking markers that are coupled to the cutting tool. Trackingthe spatial positioning of the end effector portion of the cutting toolmay comprise monitoring the positions of one or more joints of amechanical tracker linkage that is coupled to the cutting tool. Themethod may further comprise intercoupling a mechanical tracker linkagebetween the bone and the handheld manipulator to facilitate monitoringof the three dimensional relative spatial relationship between the boneand the handheld manipulator. Intercoupling may comprise removablycoupling at least one end of the mechanical tracker with a kinematicquick-connect fitting. The method may further comprise modulating thetool path automatically based at least in part upon potential fieldanalysis or alternate heuristic algorithm, such as a spatial statemachine heuristic. Modulating the tool path may comprise executingmotion compensation based upon the potential field analysis or alternateheuristic algorithm. Modulating the tool path may comprise hapticallyresisting motion of the handheld manipulator.

Another embodiment is directed to a robotic surgery method for cutting abone of a patient, comprising: characterizing the geometry andpositioning of the bone; manually moving a handheld manipulator, thehandheld manipulator operatively coupled to a bone cutting tool havingan end effector portion, to cut a portion of the bone with the endeffector portion; and automatically compensating for aberrant movementof the bone cutting tool that would place the end effector portion ofthe tool out of a desired bone cutting envelope that is based at leastin part upon the image information, while allowing the bone cutting toolto continue cutting one or more portions of the bone. Characterizing thegeometry and position of the bone may comprise analyzing imageinformation acquired from the bone. The method may further compriseacquiring the image information using a modality selected from the groupconsisting of: computed tomography, radiography, ultrasound, andmagnetic resonance.

DETAILED DESCRIPTION

Referring to FIG. 1A, as discussed briefly above, it may be useful incertain surgical scenarios to utilize a handheld manipulator (2) coupledto a tool (28) such as a bone removal tool, in interventions involvingvarious aspects of the human skeleton (50). For example, as shown moreclosely in FIG. 1B, it may be useful to use a handheld manipulator (2)and associated tool (28) with an end effector distal portion (30) suchas a bone burring or osteotomy tip to remove portions of a femur (64) ofa patient in a joint resurfacing operation, such as those involvingprostheses available from MAKO Surgical Corporation of Fort Lauderdale,Fla. The illustrative configuration comprises the handheld manipulator(2) with a motion compensation assembly (6) that couples the tool (28)and an associated tool driver (24) to the main manipulator housing (16).

In embodiments wherein activity of the motion compensation assembly (6)is to be utilized to assist in preventing aberrant bone removal toolpathways that stray from a predetermined bone removal plan or“envelope”, it is desirable to understand where both the subject tissuestructure (here the femur 64) and the tool (28) are relative to somecommon coordinate system, such as a global coordinate system (66) of theoperating room. Such an understanding may be developed using variousposition sensing or tracking technologies.

Referring to FIG. 1C, in one embodiment, an optical tracker system (70),such as those available from Northern Digital, Inc. of Ontario, Canada,may be utilized to monitor the real or near-real time position of one orboth of the handheld manipulator (2) and bone (64), subject to therequirement that the monitored structures be outfitted with markers(such as groups of small spheres or disks; not shown) that reflect lightemitted from the optical tracking system (70). A controller (14), suchas a computer, processor, or microcontroller, which may reside, forexample, in a personal computer or similar computing apparatus, may becoupled, via electronic leads (72, 72) to the tracking system (70) andhandheld manipulator (2), and configured to operate motors within themanipulator (2) to assist with avoidance of bone removal pathways thatmay be attempted by an operator, as discussed in further detail below. Adisplay (68) may be coupled via another lead (76) to the controller andconfigured to show an operator a graphical user interface featuringinformation regarding the subject anatomy and interaction between theanatomy and the subject tools. Any of the leads described herein (forexample, 72, 74, 76) may be replaced in other embodiments with wirelessconnectivity to avoid physical lead tethering.

In other embodiments, other spatial tracking technologies, such as thosebased upon ultrasonic or ultra-wide-band transducer monitoring (forexample, to analyze time-of-flight information for various locations ona handheld manipulator 2), may be utilized to characterize the spatialpositioning of a handheld manipulator and associated tool (28) in nearreal or real time.

Referring to FIG. 1D, another embodiment is illustrated wherein anoptical tracking system (70) may be utilized to track the spatialpositions of one or more of the subject tissue structure (64) and arobotic arm (80) which may be utilized to support the tool (28) duringat least a portion of the surgical procedure. The embodiment of FIG. 1Dfeatures a robotic surgery system having a base assembly that comprisesa controller (78) which is operatively and driveably coupled to therobotic arm (80) as well as the tool (28). An electronic lead (74)couples the tool (28) with the controller base, another electronic lead(72) couples the optical tracking system (70) with the controller base(78), and another electronic lead (76) couples the controller base (78)to a display (68) configured to show a graphical user interface to anoperator, as in systems available from MAKO Surgical Corporation of Ft.Lauderdale, Fla., such as those disclosed in U.S. Pat. No. 8,010,180,which is incorporated by reference herein in its entirety. With thecontroller base (78) grounded and registered relative to the globalcoordinate system (66) and markers in place coupled to the subjectanatomy (64) as well as the tool (28) and/or a portion of the roboticarm (80), the controller may be utilized to monitor thethree-dimensional positions of the tool (28) relative to the anatomy(64) with a high level of precision, and to allow an operator, viacontrolled active and passive robotic arm (80) joint control activity,to manipulate the tool (28) into desirable positions within the desiredbone cutting envelope. One of the possible downsides of such aconfiguration is the inertial and kinematic overhead associated withhaving the tool (28) coupled to a relatively large robotic arm (80). Inone embodiment, the robotic arm (80) may be configured to compensate, atleast in part, for the effects of gravitational acceleration (socalled“gravity compensation), thereby reducing the loads that need be appliedin certain directions to move the tool (28). Such gravity compensationmay be accomplished using motors and sensors within the intercoupledrobotic arm (80), which are capable of monitoring the positioning of thearm (80) and intercoupled tool relative to the acceleration of gravity,and counteracting the effects of gravity upon the arm and tool. Gravitycompensation mechanisms such as the depicted robotic arm configuration(80), or such as more simplistic mechanisms such as gravity-counteringlinear or nonlinear spring mechanisms, may be applied in the embodimentsdescribed in reference to FIGS. 1E and 1F as well.

Referring to FIG. 1E, another embodiment is depicted wherein a handheldmanipulator (2) may be utilized in a tissue structure (64) intervention,and wherein the spatial positioning of the bone (64) and manipulator (2)may be monitored using two mechanical tracker assemblies (90, 92), eachof which has a proximal end coupled to a base structure (82, 84) thathas a known position and orientation relative to a coordinate systemsuch as the global coordinate system (66) of the operating room. Thedistal end of the first tracker assembly (90) is coupled to the bone(64) using a bone coupling member which may be fastened to the bone withone or more pins as shown, and removably coupled to the distal portionof the tracker assembly (90) with a coupling interface (122) that maycomprise a kinematic quick connect fitting or interface, as described infurther detail below, and also in U.S. patent application Ser. No.13/276,048, filed simultaneously, which is incorporated by referenceherein in its entirety. A similar coupling interface (124) may beutilized to couple the proximal end of the mechanical tracker (90) tothe base structure (82). As described in the aforementioned incorporatedby reference disclosure, the depicted mechanical tracker (90) embodimentmay comprise four joints (100, 102, 104, 106) and three elongate members(94, 96, 98), as well as sensors configured to monitor the rotations ofthe joints (100, 102, 104, 106). A similar second mechanical tracker(92) comprising four joints (114, 116, 118, 120), three elongate members(108, 110, 112), and similar joint rotation sensors may be utilized totrack the position and orientation of the handheld manipulator (2).Electronic leads (88, 86) from the trackers (90, 92) may be utilized toallow the controller (14) to process the pertinent signals andcalculate, as well as display (68), the relative spatial positions andorientations of the subject tissue structure (64) and tool (28) relativeto each other. Further, as described in greater detail below, motorswithin the handheld manipulator (2) may be controllably actuated toprovide motion compensation to at least partially defeat certainaberrant motions (i.e., aberrant because they stray from a predetermineddesired cutting envelope) attempted by virtue of manual commands placedupon the handheld manipulator.

Referring to FIG. 1F, in another embodiment, a single mechanical tracker(90) may be utilized to track the positions and/or orientations of themanipulator (2) and tool (28) relative to the subject anatomy (64), withinherent registration by virtue of the connectivity between the twoelements. The proximal end of the mechanical tracker (90) may be coupledto a coupling interface member (132) of the handheld manipulator (2)using a removably attachable kinematic quick connect interface;similarly, the distal end of the mechanical tracker (90) may be coupledto the bone coupling member (130) with a removably attachable kinematicquick connect interface.

With each of the embodiments shown in FIGS. 1C-1F, the controller (14)may be utilized along with the various position/orientation sensingelements, to monitor the three dimensional spatial relationships of thesubject anatomy and manipulator/tools. This understanding may beharnessed in a motion compensation configuration wherein attempted(either purposefully or accidentally) tool movement commands manually atthe manipulator may be at least partially defeated usingelectromechanical features of the manipulator to keep the tool on trackand within a previously determined desired tissue cutting envelope. Inother words, an aspect of closed loop control may be employed to keepthe tool within the prescribed bounds.

For example, referring to FIG. 2A, a desired bone cutting envelope (134)is illustrated. Such a bone cutting envelope (134) may, for example,represent a volume of bone to be removed based on preoperative planningwith regard to the patient's anatomy and an orthopaedic resurfacingprosthesis of particular geometry. In an ideal world, an operator wouldbe able to utilize a manipulator such as a handheld manipulator tosculpt precisely within the bone cutting envelope (134) so that theprosthesis fits precisely against the prepared bony surface. Inactuality, various factors may affect an operator's ability to commandthe tool precisely within the desired bone cutting envelope (134), suchas tremors of the operator (which tend to occur at relatively highfrequencies, such as frequencies greater than about 1 Hz (for example,frequencies between about 1 Hz and about 12 Hz), and at relatively lowamplitudes) and/or accidental or unplanned bulk motions of the operatoror the patient (which tend to occur at relatively low frequencies, suchas frequencies below 1 Hz, and at various amplitudes, includingrelatively high amplitudes).

For example, referring to FIG. 2B, a desired bone cutting envelope (134)is shown with a dashed line, and an actual commanded tool path (136) isshown with a solid line. Small tremor-like activity is illustrated, forexample, with the relatively low amplitude, and relatively highfrequency, departures (140) from the desired bone cutting envelope(134). An accidental bulk motion of the patient or operator isillustrated (138) as a relatively high amplitude, lower frequencyaberration or departure from the planned envelope (134). To addresscommands such as these which, absent some mitigation, would take thetool outside of the desired bone cutting envelope (134), a controllermay be configured to react to such commands quickly by automaticallymoving the tool back toward, and preferably back within, the preferredbone cutting envelope (134). FIGS. 3A-3M illustrate aspects of ahandheld manipulator system configured to not only deflect the toolcontrollably in pitch and/or yaw relative to a longitudinal axis (142)of the tool (28), but also to insert or withdraw the tool substantiallyparallel to that axis (142).

In one embodiment, a controller may be configured to modulate thecutting velocity of a cutting tool, such as an angular velocity of arotary bone cutting burr, or the oscillatory velocity and/or frequencyof a reciprocating cutting tool, such as a reciprocating bone saw, basedat least in part upon the location of the tool relative to the desiredbone cutting envelope. For example, in one embodiment, the controllermay be configured to generally reduce the angular velocity, oscillatoryvelocity, or oscillatory frequency of the cutting tool when the tool ismoved adjacent an edge of the desired bone cutting envelope. In anotherembodiment, a controller may be configured to modulate the cuttingvelocity (i.e., angular velocity, oscillatory velocity, or oscillatoryfrequency) of the cutting tool based at least in part upon the locationof the tool within a predetermined workspace for the handheldmanipulation. In other words, the controller may be configured such thatthe angular velocity, oscillatory velocity, or oscillatory frequency isgenerally reduced when the tool is moved toward the edge of thepredetermined workspace.

Referring to FIG. 3A, a side view of a handheld manipulator (2)configuration is depicted, wherein a frame assembly (4) extendingthrough a housing (16) has a proximal coupling interface member (132)configured to be easily couplable to a mechanical tracker or othermember. Extending distally of the housing (16) are three elongatestructural members (two shown—8, 10; shown in other figures—12) whichare coupled to a motion compensation assembly (6), which is coupled to atool drive assembly (24). The tool drive assembly (24) may comprise amotor and motor housing or motor coupling structure, and is movablycoupled to the tool (28). Upon manual depression of the trigger (238)operatively coupled to the housing (16), a motor of the tool driveassembly (24) may cause the tool (28) or the end effector portionthereof (30; such as a bone burring tip) to rotate at a controlledangular velocity selected to remove bony material from a substrate. FIG.3B illustrates a different orthogonal view of the assembly of FIG. 3A,to illustrate that the motion compensation assembly (6) and associatedelongate structural members (two shown—8, 10; shown in other figures—12)and assemblies related thereto, may be utilized to controllablyinsert/retract (144) and/or pitch and or yaw the tool (28)omnidirectionally (146, 148, 150) in response to controlled activity ofassociated actuators. The combination of insertion/retraction control(can also be called “z-axis” control given a z-axis coaxial with thelongitudinal axis 142 of the tool), pitch/yaw control, roll control withthe motor (24) configuration, and x and y axis (relative to the z-axis)control with the frame linkage (6) assembly provides 6-degree-of-freedomcontrolled movement at the end effector tip portion (30), and therefore6-degree-of-freedom motion compensation under the paradigms describedherein.

Referring to FIG. 3C, another orthogonal view illustrates the thirdelongate structural member (12), along with a motion compensationcoupling base (152) that is movably coupled to each of three motioncompensation linkage assemblies (32, 34, 36) that are coupled to theelongate structural members (8, 10, 12). FIG. 3D shows the housing (16)deconstructed from the rest of the handheld manipulator assembly. FIG.3E shows the frame assembly (4) that fits inside of the housing (16) ofFIG. 3D, the frame assembly comprising three motors operatively coupledto the three elongate structural members (8, 10, 12) and configured tocontrollably and independently retract or insert these members inresponse to motion compensation commands from the controller (14), whichmay be combined through the motion compensation assembly (6) toomnidirectionally pitch/yaw the tool, as well as simultaneously insertor retract the tool.

Referring to FIG. 3F, each of the elongate structural members (10); notshown are identical subassemblies for 8 and 12) is coupled into amovable lead screw assembly (166) comprising a threaded member (168)that moves the elongate member (10) and guide base member (242) axiallyrelative to a screw that is threaded through the threaded member (168)and controllably twisted in one of two directions by an associatedmotor, to either insert or retract the elongate member (10). The distalportion of the movable lead screw assembly (166) comprises two rotatablecoupling interfaces (158, 160) configured to be interfaced with twoapertures (162, 164) formed in the paired motion compensation linkage(34), which has two additional similar rotatable coupling interfaces(154, 156). The relative motion provided by the linkages (32, 34, 36)assist in facilitating omnidirectional motion at the motion compensationcoupling base (152), which is fixedly coupled to the tool drive assembly(24). FIG. 3H shows a different view of the assembly of FIG. 3G with theexception that one of the motion compensation linkage assemblies (36—notshown) has been removed to illustrate that a rotational degree offreedom is provided in the linking with the motion compensation couplingbase (152), as shown, for example, with the two illustrated axes ofrotation (170, 172) for two of the motion compensation linkageassemblies (36—not shown, 34 shown).

Referring to FIG. 3I, a frame assembly (4) is shown with all threeelongate structural members (8, 10, 12) movably coupled thereto. A firstlead screw assembly (38) comprises the first elongate structural member(8), the first guide base member (240), and a first lead screw (176)that is coupled to a first driven pulley (178) movably coupled to amotor (not shown) by a first belt (44). FIG. 3J shows a partial assemblyof the more complete assembly of FIG. 3I to illustrate the screw (176),driven pulley (178), and motorized insertion/retraction (174) providedby the motor (236) that drives the belt and associated driven pulley(178) in one of two directions subject to electronic commands from acontroller (14). FIG. 3K shows a bottom view to illustrate that thereare three similar mechanisms to independently and simultaneously controlinsertion or retraction of each of the three elongate structural members(8, 10, 12), and therefore, as described above, provide omnidirectionalpitch/yaw as well as insertion/retraction of the motion compensationcoupling base (152) and associated tool drive assembly (24) and tool(28). Three motors (not shown), which may be equipped with gearboxes,underly each of three motor pulleys (190, 192, 194). Each of the motorpulleys is coupled to a driven pulley (178, 246, 248) using a belt (44,46, 48), and each driven pulley (178, 246, 248) is coupled to a leadscrew (176, 186, 188). Each lead screw (176, 186, 188) is coupled to athreaded member, guide base member, and elongate structural member suchthat rotation of each motor causes rotation of the lead screw andinsertion or retraction of the pertinent elongate structural member.

In another embodiment, one or more of the belt drive rotary motiontransfer configurations shown in the embodiment of FIGS. 3I-3K may bereplaced with a gear to gear mechanical interface (i.e., a “gear drive”configuration as opposed to a “belt drive” configuration), wherein adrive belt is avoided in each gear drive interface by having directmechanical teeth interfacing. The belt drive configurations may bedesired for the mechanical and acoustic damping that accompanies a beltdrive interface, as well as the geometric efficiency afforded by beltdrive interfaces, wherein driving and driven capstans may be separatedand remain driveable coupled without geartrains therebetween to bridgegeometric gaps. Any transmission means described herein may be replacedin an alternate embodiment with a different transmission means, with thesame purpose of transferring motor torque to the lead screws (or other)actuations members.

Referring to FIG. 3L, the proximal coupling interface member (132), aswell as other coupling interface members (see, for example, theinterfaces 122, 124, 126, 128) may comprise a kinematic quick connectfitting, as described in the aforementioned incorporated by referencedisclosure, which comprises one or more magnetic elements (192, 194,196) which may have polarities organized to only allow one orientation,and to also facilitate a relatively simple disconnect via a relativelysmall, high-impulse load applied to the interface. One or more valleyfeatures (198, 200, 202) assist in providing a kinematic interface onlycapable of one predictable orientation.

Referring to FIGS. 4A-5C, various processes for utilizing the subjectconfigurations in surgery are illustrated. As shown in FIG. 4A, afterpreoperative imaging (such as computed tomography, radiography,ultrasound, magnetic resonance, or other medical imaging) (204), apreoperative cutting plan may be created, and this may define a desiredtissue cutting envelope (206). Surgical access may be created (208), thetargeted tissue structure and cutting tool registered (210) relative toa coordinate system, and a manipulator operated to cut and/or removeportions of bone or other tissue (212). During such operation, acontroller may be configured to monitor the positioning of the bone andcutting tool, to detect aberrant relatively high-frequency movementcommands from the operator (i.e., such as those that may come fromtremor activity of the operator), and to continue cutting while alsodefeating at least portions of such aberrant commands, to facilitatekeeping the cutting tool within the envelope (214). After tissue removalhas been completed in accordance with the cutting envelope (216), aprosthesis, such as a joint resurfacing prosthesis, a screw, or otherprostheses, may be installed (218). Intraoperative imaging, such asfluoroscopy, radiography, ultrasound, computed tomography, and/ormagnetic resonance may be conducted to confirm positioning of variousstructures (220), and the surgical access may be closed (222).

In another embodiment, the preoperative cutting plan and definition of atissue cutting envelope may be conducted without preoperative imaging;instead, the positioning and geometry of the bone and other associatedtissue may be determined using non-imaging spatial characterizationtechniques. For example, in one variation, the spatial positioning of aseries of bony anatomic landmarks may be determined using a probeoperatively coupled to a system capable of establishing probe positionsrelative to a global or local coordinate system, such as a robotic arm80 as described above, and based upon this determination and assumptionsabout the shape the various tissue structures in between the landmarkpoints (i.e., from previous patient data and/or other relatedanthropomorphic data), the positioning and geometry of the subjecttissue structure (such as a long bone) may be characterized withprecision.

Referring to FIG. 4B, an embodiment similar to that of FIG. 4A isdepicted, with the exception that a controller is configured to conductautomatic motion compensation for aberrant commands of relatively lowfrequency (i.e., such as accidental commands that may result fromoperator error, patient movement, etc), while the cutting andinterventional procedure in general is completed (224).

FIG. 4C illustrates an embodiment that combines the functionalities ofthe embodiments of FIGS. 4A and 4B, such that the controller isconfigured to conduct motion compensation for both relatively high, andrelatively low frequency aberrant commands (226), to facilitate keepingthe cutting tool within the desired bone cutting envelope.

Referring to FIG. 5A, an embodiment is illustrated wherein some stepsare similar with the embodiments of FIG. 4A, with the exception of aswitching from a first cutting tool to a second cutting tool, withmotion compensation for the second tool utilized, which in theillustrative case is part of a handheld manipulator configuration. Asshown in FIG. 5A, after surgical access has been created, a firstcutting tool is registered with the target tissue structure (228) and isoperated to cut portions of the target tissue, at least partiallyremoving the volume of bone within the desired cutting envelope (230).The first cutting tool may in one embodiment, for example, be coupled toa robotic arm, as described above in reference to FIG. 1D. A handheldmanipulator and associated tool may then be utilized (232, 234), andautomatic motion compensation conducted to mitigate relatively highfrequency aberrant movement commands, such as those which may beassociated with operator tremor (214).

Referring to FIG. 5B, an embodiment similar to that of FIG. 5A isillustrated, with the exception that a controller is configured toconduct automatic motion compensation for aberrant commands ofrelatively low frequency (i.e., such as accidental commands that mayresult from operator error, patient movement, etc), while the cuttingand interventional procedure in general is completed (224).

FIG. 5C illustrates an embodiment that combines the functionalities ofthe embodiments of FIGS. 5A and 5B, such that the controller isconfigured to conduct motion compensation for both relatively high, andrelatively low frequency aberrant commands (226), to facilitate keepingthe cutting tool within the desired bone cutting envelope.

In another embodiment, toolpath optimization in real or near-real timemay be utilized to assist an operator in cutting out a targeted volumeof tissue. For example, a tool path through the subject anatomy in theembodiments above may be controlled using automatic motion compensation,haptic resistance to particular tool positions (using, for example, anintercoupled haptic robotic arm system such as that discussed above 80in reference to FIG. 1D), or both. And while tool path optimization iswell known in certain applications such as CNC milling, wherein completeknowledge of the environment is coupled with complete control over thecutting tool, the scenario of a handheld surgical tool in the hands of asurgeon presents quite a different challenge given the fact that thesurgeon is going to significantly contribute to the tool path with hismanual control motions, and the fact that the control system generallyhas no prior knowledge of what the surgeon is going to do from a toolpath perspective. In one embodiment, potential fields may be used tocause the tool to move autonomously toward small volumes marked asattractive (i.e., voxels of bone that has been targeted for removal, butwhich has not yet been in the bone cutting tool path), and away fromsmall volumes marked as repulsive (i.e., voxels of bone that has beentargeted for removal, and which has already been in the path of the bonecutting tool). Potential fields have been used, for example, to assistwith controls paradigms for mobile robots avoiding obstacles on a floor,for example, as in Navigation of Mobile Robots Using Potential Fieldsand Computational Intelligence Means, Acta Polytechnica Hungarica Vol 4,No. 1, 2007, which is incorporated by reference herein in its entirety.In the subject embodiment, potential fields may be used to attract thetool path to uncut tissue that is to be cut under the surgical plan, andto repulse the tool path from tissue that has already been cut per thesurgical plan, or from tissue that is not to be cut per the surgicalplan—and again, the execution of such attraction or repulsion may be inthe form of the control system actively attracting or repulsing the toolfrom a particular voxel or group thereof using haptic forces imparted tothe handheld manipulator by a haptic subsystem, by the control systemactively attracting or repulsing the tool from a particular voxel orgroup thereof using the automated motion compensation configurationsdescribed above, or by both haptics and motion compensation.

Referring to FIG. 6A, a sample potential field function is shown that isbased upon a hyperbolic secant function (300) that can be used toattract or repulse the tool after the volume of tissue has beenvirtually divided into a three-dimensional mesh of voxels (302) withvalues assigned to each voxel in advance of the procedure based upon thesurgical plan for cutting and removal, as shown in FIG. 6B. Referring toFIG. 6C, a bounding volume (304) such as a sphere for a substantiallyspherical bone cutting burr (with cutting tool centerpoint labeled aselement 306), may be analyzed automatically in real or near-real time asintersecting with the voxel mesh (302); the values of the voxels in thiseffected intersecting volume may be numerically analyzed and summed inview of the potential field function (300), and the output from thissummation may be used as an input in the controls scheme to alter thetool path—either attractively or repulsively. Further, the system may beconfigured to update the voxel values with updated tool pathinformation; for example, when the tool goes through a voxel tagged asattractive per the surgical plan, it may then be tagged as repulsivesince it has already encountered the tool, and the tool pathoptimization may continue to evolve, and to help the operator to removeall of the bone or other tissue, as per the preoperative plan. Further,the voxels representative of the edge of the predetermined cuttingenvelope may be always set to have a repulsive condition. In anotherembodiment, the tool path may be modulated automatically based upon aheuristic, such as a spatial state machine heuristic.

Referring to FIG. 7, an embodiment similar to that of FIG. 4A isillustrated, with the exception that with manual operation of thehandheld manipulator (212) the control system is configured to not onlyexecute automatic motion compensation to address aberrant relativelyhigh frequency movement, but also to modulate the tool pathautomatically based upon potential field analysis, using haptics, motioncompensation, or both. Similarly, potential field analysis may be addedto any of the other abovedescribed configurations, such as thosedescribed in relation to FIGS. 4B-5C.

Various exemplary embodiments of the invention are described herein.Reference is made to these examples in a non-limiting sense. They areprovided to illustrate more broadly applicable aspects of the invention.Various changes may be made to the invention described and equivalentsmay be substituted without departing from the true spirit and scope ofthe invention. In addition, many modifications may be made to adapt aparticular situation, material, composition of matter, process, processact(s) or step(s) to the objective(s), spirit or scope of the presentinvention. Further, as will be appreciated by those with skill in theart that each of the individual variations described and illustratedherein has discrete components and features which may be readilyseparated from or combined with the features of any of the other severalembodiments without departing from the scope or spirit of the presentinventions. All such modifications are intended to be within the scopeof claims associated with this disclosure.

Any of the devices described for carrying out the subject interventionsmay be provided in packaged combination for use in executing suchinterventions. These supply “kits” further may include instructions foruse and be packaged in sterile trays or containers as commonly employedfor such purposes.

The invention includes methods that may be performed using the subjectdevices. The methods may comprise the act of providing such a suitabledevice. Such provision may be performed by the end user. In other words,the “providing” act merely requires the end user obtain, access,approach, position, set-up, activate, power-up or otherwise act toprovide the requisite device in the subject method. Methods recitedherein may be carried out in any order of the recited events which islogically possible, as well as in the recited order of events.

Exemplary aspects of the invention, together with details regardingmaterial selection and manufacture have been set forth above. As forother details of the present invention, these may be appreciated inconnection with the above-referenced patents and publications as well asgenerally know or appreciated by those with skill in the art. Forexample, one with skill in the art will appreciate that one or morelubricious coatings (e.g., hydrophilic polymers such aspolyvinylpyrrolidone-based compositions, fluoropolymers such astetrafluoroethylene, hydrophilic gel or silicones) or polymer partssuitable for use as low friction bearing surfaces (such as ultra highmolecular weight polyethylene) may be used in connection with variousportions of the devices, such as relatively large interfacial surfacesof movably coupled parts, if desired, for example, to facilitate lowfriction manipulation or advancement of such objects relative to otherportions of the instrumentation or nearby tissue structures. The samemay hold true with respect to method-based aspects of the invention interms of additional acts as commonly or logically employed.

In addition, though the invention has been described in reference toseveral examples optionally incorporating various features, theinvention is not to be limited to that which is described or indicatedas contemplated with respect to each variation of the invention. Variouschanges may be made to the invention described and equivalents (whetherrecited herein or not included for the sake of some brevity) may besubstituted without departing from the true spirit and scope of theinvention. In addition, where a range of values is provided, it isunderstood that every intervening value, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention.

Also, it is contemplated that any optional feature of the inventivevariations described may be set forth and claimed independently, or incombination with any one or more of the features described herein.Reference to a singular item, includes the possibility that there areplural of the same items present. More specifically, as used herein andin claims associated hereto, the singular forms “a,” “an,” “said,” and“the” include plural referents unless the specifically stated otherwise.In other words, use of the articles allow for “at least one” of thesubject item in the description above as well as claims associated withthis disclosure. It is further noted that such claims may be drafted toexclude any optional element. As such, this statement is intended toserve as antecedent basis for use of such exclusive terminology as“solely,” “only” and the like in connection with the recitation of claimelements, or use of a “negative” limitation.

Without the use of such exclusive terminology, the term “comprising” inclaims associated with this disclosure shall allow for the inclusion ofany additional element—irrespective of whether a given number ofelements are enumerated in such claims, or the addition of a featurecould be regarded as transforming the nature of an element set forth insuch claims. Except as specifically defined herein, all technical andscientific terms used herein are to be given as broad a commonlyunderstood meaning as possible while maintaining claim validity. Thebreadth of the present invention is not to be limited to the examplesprovided and/or the subject specification, but rather only by the scopeof claim language associated with this disclosure.

What is claimed is:
 1. A robotic surgery method for cutting a bone of a patient, comprising: characterizing the geometry and positioning of the bone; manually moving a handheld manipulator, the handheld manipulator operatively coupled to a bone cutting tool having an end effector portion, to cut a portion of the bone with the end effector portion, wherein the handheld manipulator includes a manipulator housing and an actuator assembly movably coupled between the manipulator housing and the bone cutting tool; and causing the actuator assembly to automatically move relative to the manipulator housing to maintain the end effector portion of the tool within a desired bone cutting envelope in response to movement of the manipulator housing relative to the bone.
 2. The method of claim 1, further comprising: tracking a position of the end effector portion relative to the bone cutting envelope using a tracking subsystem, wherein the tracking subsystem comprises a mechanical tracking arm having a first end and a second end; coupling the first end of the tracking arm to a coupling interface on the manipulator housing and the second end of the tracking arm to a coupling interface positioned on the bone; and wherein the mechanical tracking arm is operatively coupled to the controller to allow the controller to calculate the spatial position of the end effector relative to the bone.
 3. The method of claim 1, wherein the handheld manipulator is configured to be manually moved in a global coordinate system relative to the bone.
 4. The method of claim 1, wherein the end effector portion is configured to be moved at a preferred bone cutting velocity.
 5. The method of claim 4, further comprising modulating the cutting velocity based at least in part upon the location of the end effector portion within a desired bone cutting envelope.
 6. The method of claim 5, further comprising reducing the cutting velocity of the end effector portion when the end effector portion is moved adjacent an edge of a desired bone cutting envelope.
 7. The method of claim 1, further comprising modulating the cutting velocity of the end effector portion based at least in part upon the location of the end effector portion within a predetermined workspace of the handheld manipulator.
 8. The method of claim 7, further comprising reducing the cutting velocity of the end effector portion when the end effector portion is moved adjacent an edge of the predetermined workspace of the handheld manipulator.
 9. The method of claim 1, wherein the end effector portion is allowed to continue cutting one or more portions of the bone at the preferred cutting angular velocity while the actuator assembly automatically moves relative to the manipulator housing.
 10. The method of claim 1, wherein causing the actuator assembly to automatically move relative to the manipulator housing comprises controllably moving the cutting tool relative to the manipulator housing.
 11. The method of claim 10, wherein controllably moving comprises axially moving the cutting tool in a direction substantially coaxial with a longitudinal axis of a previous position of the cutting tool.
 12. The method of claim 10, wherein controllably moving comprises adjusting a pitch or yaw of the cutting tool relative to a longitudinal axis of a previous position of the cutting tool.
 13. The method of claim 10, wherein controllably moving comprises moving the cutting tool in two or more degrees of freedom.
 14. The method of claim 10, wherein controllably moving the cutting tool relative to the handheld manipulator comprises operating a motor.
 15. The method of claim 14, wherein operating the motor operates a lead screw mechanism operatively coupled to the motor.
 16. The method of claim 1, further comprising determining that an attempted movement is an aberrant movement.
 17. The method of claim 16, wherein determining that an attempted movement is an aberrant movement comprises tracking the spatial positioning of the bone and the end effector portion of the cutting tool.
 18. The method of claim 17, wherein tracking the spatial positioning of the bone comprises monitoring the positions of one or more optical tracking markers that are coupled to the bone.
 19. The method of claim 17, wherein tracking the spatial positioning of the bone comprises monitoring the positions of one or more joints of a mechanical tracker linkage that is coupled to the bone.
 20. The method of claim 17, wherein tracking the spatial positioning of the end effector portion of the cutting tool comprises monitoring the positions of one or more optical tracking markers that are coupled to the cutting tool.
 21. The method of claim 17, wherein tracking the spatial positioning of the end effector portion of the cutting tool comprises monitoring the positions of one or more joints of a mechanical tracker linkage that is coupled to the cutting tool.
 22. The method of claim 1, further comprising intercoupling a mechanical tracker linkage between the bone and the handheld manipulator to facilitate monitoring of the three dimensional relative spatial relationship between the bone and the handheld manipulator.
 23. The method of claim 22, wherein intercoupling comprises removably coupling at least one end of the mechanical tracker with a kinematic quick-connect fitting.
 24. The method of claim 1, further comprising modulating the tool path automatically based at least in part upon a potential field analysis.
 25. The method of claim 24, wherein modulating the tool path comprises executing motion compensation based upon the potential field analysis.
 26. The method of claim 24, wherein modulating the tool path comprises haptically resisting motion of the handheld manipulator.
 27. The method of claim 1, further comprising modulating the tool path automatically based at least in part upon a spatial state machine heuristic.
 28. The method of claim 1, wherein characterizing the geometry and positioning of the bone comprises acquiring image information regarding the bone and analyzing the image information.
 29. The method of claim 28, wherein acquiring image information uses a modality selected from the group consisting of: computed tomography, radiography, ultrasound, and magnetic resonance.
 30. The method of claim 28, further comprising creating a preoperative surgical plan based at least in part upon the image information, and utilizing the preoperative surgical plan to create the desired bone cutting envelope. 